Re: i was thinking about this..
I've noticed it seems that anyone that gets a used rocket valve and has probs with it, got it from someone that cut the valve pin too short and had recocking or velocity probs. They sell the valve because it's almost impossible to get a repair kit for them. You might try getting a repair kit before you pursue this any further otherwise you may be starting from a point where you cannot attain your goal at all no matter what you do. I would always deter anyone from buying a used rocket valve from someone that already cut the valve shaft -
The dealio with the springs is pretty much what Dex mentioned. If you use a heavier spring all it really does is makes it that much more difficult to recock the striker and if you have a misfire, the ball will most assuredly be chopped. The ultimate IMO is leaving the SRP opened as much as possible and using the lightest spring possible. That makes a nice dwell, recocking is simple and if there's a misfire, the bolt is less likely to chop the ball. Mine will just stop on the ball in this configuration -